In some industries, such as the aircraft industry, manufactured parts must be inspected to ensure that the size and the shape of each part, as well as the placement of various part features such as apertures, corners and trim, conform to the nominal or engineered design. Parts may experience a small amount of warping or other changes in shape during or after the manufacturing process. Such changes in the shapes of parts may, not render the parts defective or unusable, but can complicate the inspection process by introducing variances between certain dimensions of the manufactured part and the engineered part design.
One way to accommodate such changes in the shape of the part during inspection is to place the part in a fixture that constrains the part to the shape of the engineered design. Unfortunately the use of fixtures can be impractical due to cost. Typically, a unique fixture must be created for each manufactured part, and each fixture may cost as much as $100,000 or more. Furthermore, the process of placing parts in fixtures is labor-intensive and is subject to certain inaccuracies, including mechanical tolerances of the fixture. These mechanical tolerances may be impacted by wear and tear due to repeated use of the fixture and may also be negatively affected by thermal expansion and contraction. If the fixture has a different coefficient of thermal expansion than the part, for example, changes in temperature may cause the fixture to expand or contract a different amount than the part, causing a good part to fail inspection or, worse yet, causing a defective part to pass inspection.
To avoid the costs associated with the use of fixtures for part verification, some manufacturers use a manual process of part verification that does not involve fixtures. Rather, human operators measure the part in a relaxed or free state. These processes are also labor-intensive and subject to human error as well as errors inherent in the inspection of deformed parts. A minor but undetected deformation, for example, may cause the radius of curvature of a part to be larger or smaller than the nominal radius of curvature, which may cause the operator to determine that one or more features, such as holes or trim, are misplaced.
The above section provides background information related to the present disclosure and is not necessarily prior art.